tray: linux - use `.cache` directory for temporary icon paths

src/core/unix/SDL_gtk.c

@@ -114,8 +114,8 @@ static bool InitGtk(void)
     SDL_GTK_SYM(gtk, libgtk, gtk, menu_item_set_submenu);
     SDL_GTK_SYM(gtk, libgtk, gtk, menu_item_get_label);
     SDL_GTK_SYM(gtk, libgtk, gtk, menu_item_set_label);
-	SDL_GTK_SYM(gtk, libgtk, gtk, menu_shell_append);
-	SDL_GTK_SYM(gtk, libgtk, gtk, menu_shell_insert);
+    SDL_GTK_SYM(gtk, libgtk, gtk, menu_shell_append);
+    SDL_GTK_SYM(gtk, libgtk, gtk, menu_shell_insert);
     SDL_GTK_SYM(gtk, libgtk, gtk, check_menu_item_new_with_label);
     SDL_GTK_SYM(gtk, libgtk, gtk, check_menu_item_get_active);
     SDL_GTK_SYM(gtk, libgtk, gtk, check_menu_item_set_active);
@@ -127,6 +127,7 @@ static bool InitGtk(void)
 
     SDL_GTK_SYM(gtk, libgdk, g, signal_connect_data);
     SDL_GTK_SYM(gtk, libgdk, g, mkdtemp);
+    SDL_GTK_SYM(gtk, libgdk, g, get_user_cache_dir);
     SDL_GTK_SYM(gtk, libgdk, g, object_ref);
     SDL_GTK_SYM(gtk, libgdk, g, object_ref_sink);
     SDL_GTK_SYM(gtk, libgdk, g, object_unref);

src/core/unix/SDL_gtk.h

@@ -80,6 +80,7 @@ typedef struct SDL_GtkContext
 		gulong (*signal_connect_data)(gpointer instance, const gchar *detailed_signal, GCallback c_handler, gpointer data, GClosureNotify destroy_data, SDL_GConnectFlags connect_flags);
 		void (*object_unref)(gpointer object);
 		gchar *(*mkdtemp)(gchar *template);
+		gchar *(*get_user_cache_dir)(void);
 		gpointer (*object_ref_sink)(gpointer object);
 		gpointer (*object_ref)(gpointer object);
 		void (*object_get)(gpointer object, const gchar *first_property_name, ...);

src/tray/unix/SDL_tray.c

@@ -153,15 +153,11 @@ struct SDL_TrayEntry {
     SDL_TrayMenu *submenu;
 };
 
-/* Template for g_mkdtemp(). The Xs will get replaced with a random
- * directory name, which is created safely and atomically. */
-#define ICON_DIR_TEMPLATE "/tmp/SDL-tray-XXXXXX"
-
 struct SDL_Tray {
     AppIndicator *indicator;
     SDL_TrayMenu *menu;
-    char icon_dir[sizeof(ICON_DIR_TEMPLATE)];
-    char icon_path[256];
+    char *icon_dir;
+    char *icon_path;
 
     GtkMenuShell *menu_cached;
 };
@@ -188,13 +184,13 @@ static bool new_tmp_filename(SDL_Tray *tray)
 {
     static int count = 0;
 
-    int would_have_written = SDL_snprintf(tray->icon_path, sizeof(tray->icon_path), "%s/%d.bmp", tray->icon_dir, count++);
+    int would_have_written = SDL_asprintf(&tray->icon_path, "%s/%d.bmp", tray->icon_dir, count++);
 
-    if (would_have_written > 0 && ((unsigned) would_have_written) < sizeof(tray->icon_path) - 1) {
+    if (would_have_written >= 0) {
         return true;
     }
 
-    tray->icon_path[0] = '\0';
+    tray->icon_path = NULL;
     SDL_SetError("Failed to format new temporary filename");
     return false;
 }
@@ -254,29 +250,47 @@ SDL_Tray *SDL_CreateTray(SDL_Surface *icon, const char *tooltip)
     SDL_Tray *tray = NULL;
     SDL_GtkContext *gtk = SDL_Gtk_EnterContext();
     if (!gtk) {
-        goto error;
+        goto tray_error;
     }
 
     tray = (SDL_Tray *)SDL_calloc(1, sizeof(*tray));
     if (!tray) {
-        goto error;
+        goto tray_error;
+    }
+
+    const gchar *cache_dir = gtk->g.get_user_cache_dir();
+    if (!cache_dir) {
+        SDL_SetError("Cannot get user cache directory: %s", strerror(errno));
+        goto tray_error;
+    }
+
+    char *sdl_dir;
+    SDL_asprintf(&sdl_dir, "%s/SDL", cache_dir);
+    if (!SDL_GetPathInfo(sdl_dir, NULL)) {
+        if (!SDL_CreateDirectory(sdl_dir)) {
+            SDL_SetError("Cannot create directory for tray icon: %s", strerror(errno));
+            goto sdl_dir_error;
+        }
     }
 
     /* On success, g_mkdtemp edits its argument in-place to replace the Xs
      * with a random directory name, which it creates safely and atomically.
      * On failure, it sets errno. */
-    SDL_strlcpy(tray->icon_dir, ICON_DIR_TEMPLATE, sizeof(tray->icon_dir));
+    SDL_asprintf(&tray->icon_dir, "%s/tray-XXXXXX", sdl_dir);
     if (!gtk->g.mkdtemp(tray->icon_dir)) {
         SDL_SetError("Cannot create directory for tray icon: %s", strerror(errno));
-        goto error;
+        goto icon_dir_error;
     }
 
     if (icon) {
         if (!new_tmp_filename(tray)) {
-            goto error;
+            goto icon_dir_error;
         }
 
         SDL_SaveBMP(icon, tray->icon_path);
+    } else {
+        // allocate a dummy icon path
+        SDL_asprintf(&tray->icon_path, " ");
     }
 
     tray->indicator = app_indicator_new(get_appindicator_id(), tray->icon_path,
@@ -293,7 +307,13 @@ SDL_Tray *SDL_CreateTray(SDL_Surface *icon, const char *tooltip)
 
     return tray;
 
-error:
+icon_dir_error:
+    SDL_free(tray->icon_dir);
+
+sdl_dir_error:
+    SDL_free(sdl_dir);
+
+tray_error:
     if (tray) {
         SDL_free(tray);
     }
@@ -311,8 +331,10 @@ void SDL_SetTrayIcon(SDL_Tray *tray, SDL_Surface *icon)
         return;
     }
 
-    if (*tray->icon_path) {
+    if (tray->icon_path) {
         SDL_RemovePath(tray->icon_path);
+        SDL_free(tray->icon_path);
+        tray->icon_path = NULL;
     }
 
     /* AppIndicator caches the icon files; always change filename to avoid caching */
@@ -321,7 +343,8 @@ void SDL_SetTrayIcon(SDL_Tray *tray, SDL_Surface *icon)
         SDL_SaveBMP(icon, tray->icon_path);
         app_indicator_set_icon(tray->indicator, tray->icon_path);
     } else {
-        *tray->icon_path = '\0';
+        SDL_free(tray->icon_path);
+        tray->icon_path = NULL;
         app_indicator_set_icon(tray->indicator, NULL);
     }
 }
@@ -714,12 +737,14 @@ void SDL_DestroyTray(SDL_Tray *tray)
         DestroySDLMenu(tray->menu);
     }
 
-    if (*tray->icon_path) {
+    if (tray->icon_path) {
         SDL_RemovePath(tray->icon_path);
+        SDL_free(tray->icon_path);
     }
 
-    if (*tray->icon_dir) {
+    if (tray->icon_dir) {
         SDL_RemovePath(tray->icon_dir);
+        SDL_free(tray->icon_dir);
     }
 
     SDL_GtkContext *gtk = SDL_Gtk_EnterContext();